MLS quiz cards Flashcards

Question

Which of the following is not a potential cause of allele dropout? *Mutations in the forward primer binding site *Mutations in the reverse primer binding site * Failed PCR * Poor quality template

Answer 1

Allele dropout occurs when one allele is disproportionately amplified over the other. If the PCR were to fail, there wouldn't be amplification of either allele. Therefore, Failed PCR is the correct answer. Mutations in the forward or reverse primer binding sites of one allele may lower the affinity of the template to the primers, thus decreasing the amplification of that allele. Starting with a poor-quality sample may also decrease the amplification of one allele.

Answer 2

KRAS is the most commonly mutated oncogene seen in cancers. TP53 is seen in up to 50% of cancers, but it is a tumor suppressor gene, not oncogene. The remaining choices are found in high prevalence but only in certain types of cancers: BRCA is seen in breast & ovarian cancers, and ATM with ataxia telangiectasia.

Answer 3

The effect of anticoagulant is too great to be ignored if the hematocrit value is greater than 55%, such as in cases of polycythemia. At this hematocrit concentration, the plasma volume is lower, and the excess citrate binds more calcium ions required for calcium-dependent clotting assays. This creates falsely prolonged clotting times affecting the PT & PTT test. The correction formula used to adjust the citrate to blood ratio is: Volume of Sodium Citrate = (1.85X10^-3)x(100- Pt HCT) x volume of whole blood drawn

Answer 4

The regimen calls for weekly phlebotomy early in treatment to remove about 500mL of blood per treatment. Maintenance phlebotomist are required about every 3 months for life.

Answer 5

The correct answer is Salmonella. Salmonella (all serotypes) are facultative anaerobic, motile, Gram-negative rods commonly isolated from the intestines of humans & animals. Identification is primarily based on the ability of the organism to use citrate as the sole carbon source & lysine as nitrogen source in combination with H2S. Klebsiella species &Escherichia species will have yellow colonies on HE agar indicating no H2S production. Yersinia species will have salmon colonies on HE agar indicating no H2S production.

Answer 6

The correct answer is Alpha thalassemia silent carrier, in this form there is no anemia manifested. However, clues, that this disorder may be present can be found by exhibiting a slight decrease in the MCV & MCHC. Alpha thalassemia minor patients typically have a mild anemia with a decrease in MCV & MCHC seen. Alpha thalassemia intermedia is the second most sever expression of the disease. Patients with Hemoglobin H disease exhibit a variable degree of microcytic, hypochromic anemia. patients may go into a hemolytic crisis during infection. Alpha thalassemia major, is the most sever expression of alpha thalassemia & is a lethal disease where infants die in utero or soon after birth.

Answer 7

The correct answer is that it can be used in patients with active TB disease symptoms. In addition, an IGRA method should not be used in children younger than 5yrs. IGRAs testing is preferable for patients who have received a BCG vaccination (either as a vaccine or for cancer therapy). Prior BCG vaccination does not cause false-positive IGRA test results. IGRAs can be used instead of purified protein derivative (PPD) skin test. It is recommended over TB skin testing in individuals 5yrs and older and who have low or moderate risk of disease progression. IGRAs cannot differentiate latent TB from active TB infection.

Answer 8

The patient's test results & symptoms are consistent with type 1 diabetes, which has been associated with HLA-DR3 allele. While HLA alleles are not diagnostic of any condition, strong correlations have been shown between having certain HLA alleles & disease.

Answer 9

The culture contains three organisms, all of which can be potential UT pathogens. One or two pathogens in culture will be identified, but three indicate contamination from the collection. All three pathogens are also showing significant quantities (>10,000 CFU/mL) and thus performing sensitivity on any of these can cause inappropriate treatment for the patient. Even though the E.coli is predominant ( colony count is greater than the others), the other organisms are in a significant quantity for workup & cannot be ignored in the assessment of contamination. E.faecalis is technically in a greater quantity than Klebsiella pneumonaie and can be urinary pathogen, so it should not be listed as a contaminant over the Klebsiella pneumoniae. Urine cultures are not rejected due to contamination, they are reported with quantity & possible contamination due to increased number of organisms. Rejection of specimens occurs prior to the culture set up for any inappropriate sources or incorrect handling or storage procedures that may have occurred.

Answer 10

A rating scale with detailed descriptions of traits is the least subjective evaluation tool for direct observations. While all four choices leave room for the common evaluation errors a detailed description of each trait eliminates some of the subjectivity in the evaluation process. An anecdotal record is a written description of the student's behavior written from the point of view of the evaluator, which is very subjective. The checklist is a list of statements describing the behaviors or tasks that the student must demonstrate & the evaluator decides if the student was successful or not. A rating scale with general descriptions of traits is a quick & easy form to fill out but it leaves too much room for subjectivity in the evaluation process.

Answer 11

The diagnostic testing used for diabetes during pregnancy is different than the diagnosis of diabetes for a non-pregnant adult. There are different screening test for gestational diabetes & an oral glucose tolerance test (OGTT) is used to confirm the diagnosis. All non-diabetic pregnant women should be screened at 24-28 weeks gestation. Screening is done using the 50 g OGTT. A plasma glucose= 140mg/mL (7.7 mmlo/L) at an hour after the glucose ingestion, indicates definitive testing is needed using 100g, 3-hour OGTT.

Answer 12

The correct answer is F2. F2 is the coagulation factor gene that encodes for prothrombin. Mutations in this gene will lead to an excess production of prothrombin, which increases the risk of blood clots. F1 is fibrinogen, which can lead to an increased risk of bleeding or clotting, depending on whether too little or too much is produced. F3 is tissue factor, & F5 is proaccelerin, where decreases can also lead to bleeding, & altered protein can lead to Factor V Leiden.

Answer 13

The cumulative dilution factor in any tube in a dilution series is determined by multiplying the dilution factors of all previous tubes in series, and the calculation also includes the tube in question. Therefore, dilution factor (in series) = tube #1's dilution factor X tube#2's dilution factor...X tube# n's dilution factor. The dilution in any individual tube can be determined by the simple formula: Dilution= sample volume/(sample volume+Diluent Volume). The dilution factor is the reciprocal of the dilution. In the first tube the individual dilution ratio would be 1:11. The individual ratios in each of the remaining four tubes is 1:4 in each one. However, the question asks for the cumulative dilution ratio in tube number 5. This can be easily determined by multiplying all the dilution factors together as follows: 11 X 4 X 4 X 4 X 4 = 2816 Thus the correct answer is 2816

Answer 14

The correct answer is Cefazolin. Cefazolin is part of the Cephalosporin family & part of the beta-lactam antibiotics with the Penicillins. Cephalosporin have a species range of both aerobic & anaerobic Gram-positive & Gram-negative species. The main target for these antibiotics are penicillin-binding proteins, which inhibit the cross-linking in peptidoglycan in the cell wall of the organism. This inhibition results in cell lysis and cell death.

Answer 15

MALDI-TOF is the correct answer because the name describes its methodology (Matrix-Assisted Laser Desorption Ionization Time of Flight mass spectrometry). With this methodology, an organism will be placed directly onto a plate & a chemical matrix will be applied. Afterwards, a laser will be applied to the sample & the matrix will absorb the energy creating an ion cloud.These ions will travel through a tube called a flight tube. The lighter ions will travel faster through the tube to the detector while the heavier ions will travel slower. The detector will measure the time of flight & report out a mass spectrum. This spectrum will be compared to other spectrums within the data library for identification.

Answer 16

Clostridium perfringens is an anaerobic organism that is known to cause gas gangrene, food poisoning, & necrotizing enteritis. The identification of this organism begins with the appearance of a Gram-positive, spore- forming bacillus that produces a double-zone of beta-hemolysis on blood agar.

Answer 17

the correct answer is AHG detects antibody already sensitized to red cells. In the Direct Antiglobulin (DAT), AHG is added to patient cells after sufficient washing. This means that if a positive reaction occurs, the AHG is binding to the antibody (and/or complement proteins) already bound tot he patient RBC. Thus, it is a test to determine if in-vivo RBC sensitization has taken place. In-vivo antibody sensitization can take place during clinically significant events such as alloantibody formation& delayed transfusion reactions, autoimmune hemolytic anemia, HDFN, or drug-related mechanisms.

Answer 18

The correct answer is TP53. TP53 is a tumor suppressor gene, whose normal function is to stop cell division, but when mutated will allow for continual replication. HER2 is an oncogene associated with breast cancer, while ROS1 is seen in lung cancer, & RET in multiple endocrine neoplasia syndrome.

Answer 19

With a swab for culture & Gram stain, the culture plates should always be inoculated first to ensure that they do not become contaminated, and the slide set up last. When setting up a slide for Gram stain from a swab, it is important to roll the swab across the slide. This will ensure that the specimen is deposited evenly on the slide and maintain the integrity of the cell shape and morphology.

Answer 20

The correct answer is Penicillin. MacConkey agar is a selective & differential medium. It selects for Enterobacteriaceae and other gram-negative bacilli using bile salts and crystal violet present in the medium, which inhibit gram-positive organisms. The medium is differential because it contains lactose, which will differentiate lactose fermenting gram-negative bacilli from non-lactose fermenting gram-negative bacilli. Lactose fermenters will appear pink on agar, and non-lactose fermenters will appear clear.

Answer 21

Except for the liver, each of the sites listed above are areas where hematopoiesis occurs in adults. The yolk sac, liver, & spleen are sites of hematopoiesis during fetal months.

Answer 22

The production of a blue or purple color on the test pad of an Ictotest be interpreted as positive for bilirubin.

Answer 23

The correct answer is 4 beta chains. Hemoglobin H is a tetramer made of 4 beta chains. Hemoglobin H occurs when there is very limited alpha chain availability used to make normal hemoglobin A. Hemoglobin h forms in those affected with alpha thalassemia major as well as in people with the combination of two-gene deletion alpha thalassemia and hemoglobin Constant Spring. 2 alpha, 2 betas is normal adult Hgb A 2 alpha, 2 gammas is fetal hemoglobin Hgb F 4 alpha chains cannot form a tetrad because they are highly insoluble & precipitate within the cell.

Answer 24

Assessment of the status of amniotic fluid phospholipids has become important in determining fetal lung maturity. Pulmonary surfactant is a mixture of lipids, proteins, & glycoproteins & it is responsible for maintaining the surface tension of the alveoli preventing them from collapsing. As the fetal lungs mature, the phospholipid levels in the amniotic fluid increase, especially phosphatidylglycerol (PG) & phosphatidylcholine (lecithin). Another phospholipid, sphingomyelin has a constant amniotic concentration during pregnancy. It has been documented that the ratio of lecithin to sphingomyelin (L/S ratio), with respect to pediatric gestational age, is a reliable predictor of fetal lung maturity.